xv. 4 De Leon: Balantidium Haughwouti 397 



fresh specimen, at its junction with the middle third convex 

 superiorly, dividing abruptly, the finer granular and the coarsely 

 granular cytoplasm lying posterior to it. This constitutes the 

 upper limit of the latter. At the extremities of this line may be 

 observed, in favorable individuals, a slight constriction or in- 

 dentation of the cell wall forming some sort of a neck to the 

 individual, a fact which shows that the posterior portion is 

 more elastic and expansible laterally than the anterior which, 

 as has been previously noted, is capable of compai'atively wide 

 extension along the longitudinal axis. Moreover, this line cor- 

 responds, on the ventral surface, to the edge or ventral lip of 

 the oral excavation. 



Dorsally, at the most anterior part of this conical structure, 

 a row of membranelles is seen constantly in motion. This dorsal 

 portion constitutes the dorsal lip of the adoral excavation. It is 

 continued laterally on both sides as a thin expansion forming 

 the lateral wall through which, under deeper focus, can be seen 

 the structure of the oral apparatus. Ventrally, the median 

 anterior surface does not reach the most anterior part of the 

 animal. Instead it makes an acute dorsoposterior fold to form 

 the adoral excavation already mentioned. 



The excavation itself is funnel-shaped. At the bottom of 

 it lies the cytostome which leads into a small canal, the cyto- 

 pharynx, which, in turn, runs a short course dorsoposteriorly 

 to end blindly in the endoplasm in the vicinity of the meganu- 

 cleus. The opening between the dorsal and ventral lips measures 

 about 11.5 p. The adoral zone is well supplied with membra- 

 nelles. The cytopharynx is ciliated. The united action of 

 these membranelles and cilia, the movements of which are 

 coordinated, serves to conduct the current of food to the endo- 

 plasm. The dorsal lip of the adoral excavation is probably 

 supplied with myonemes, since the oral area can be much ex- 

 panded during active feeding. 



The posterior two-thirds part of the animal is darker and 

 coarser in appearance because it contains coarse, dark granules 

 having a greenish tinge. In recently well-fed animals these 

 granules have a deeper color, more or less bluish green, and the 

 granular appearance is overshadowed by a distinctly alveolar 

 structure. This alveolar appearance is apparently due to the 

 rapid production of a great abundance of food vacuoles, and the 

 greenish coloration would seem to be derived from the chromo- 

 phyll substance present in the bodies of the vegetable forms of 



